Royal Bank of Scotland unveiled a major shake-up of its board today, but City investors remain unconvinced this will be enough to spare chief executive Sir Fred Goodwin from the chop.

The beleaguered owner of NatWest is bringing in three new men, including British Land boss Stephen Hester, who is also a recent addition to the board of Northern Rock.

He is joined by John McFarlane, who has worked as a senior banker in Asia, Australia and the UK and Arthur Ryan, who was the top man at Prudential Financial in the US until May.

The moves are seen as a clear admission that RBS needs more banking experience on its board as it negotiates troubled waters.

It was forced to raise £12 billion from investors in the biggest rights issue in UK corporate history as it stumbled in the credit crunch. Sir Fred wrote off £6 billion of assets connected to the subprime mortgage crisis just weeks ago, increasing the pressure for him to go.

Hester, a former Abbey National finance director who helped sell the bank to Santander, is regarded as the most serious threat to Sir Fred.

David Buik at BGC Partners said Hester is "the most ambitious businessman imaginable", adding: "If a push comes to a shove Sir Fred could be history in six months. The City is irritated that RBS has overstretched itself. In essence it could take years for RBS to deliver shareholder value."

Chairman Sir Tom McKillop is also seen as under threat, especially for encouraging Sir Fred to pursue the £56 billion takeover of Dutch giant ABN Amro even after the credit crisis had begun. Larry Fish, who previously ran the US arm, and Charles Koch, another American, will stand down from the board next April.

Sir Tom said of the new recruits: "Their experience in financial services will be of great benefit to RBS given the increasingly diversified and international nature of our powerful banking franchises."

Although Hester has his problems at British Land, his 19 years of experience as an investment banker at Credit Suisse First Boston set City tongues wagging. One analyst said: "M&A is his gravy. And Sir Fred has got to go."